Process for preparing olefin oxide polymerization catalysts

ABSTRACT

In a process for the preparation of an olefin oxide polymerization catalyst comprising: 
     (i) admixing calcium, ammonia, an alkylene oxide modifier, and an organic nitrile modifier, the alkylene oxide consisting of carbon, hydrogen, and oxirane oxygen atoms and the organic nitrile consisting of carbon, nitrogen, and hydrogen atoms, at least one hydrogen atom being acidic, to form a slurry of modified calcium hexammine in ammonia; and 
     (ii) evaporating ammonia to provide a solid residue, 
     the improvement comprising: 
     aging the solid residue at a temperature in the range of about 150° C. to about 225° C.

This application is a division of our prior U.S. application Ser. No.928,974, filed July 28, 1978, now U.S. Pat. No. 4,193,892, issued Mar.18, 1980, which is a continuation-in-part of application Ser. No.902,566, filed May 8, 1978, now abandoned, which is a continuation ofapplication Ser. No. 741,013, filed Nov. 11, 1976, now abandoned.

FIELD OF THE INVENTION

This invention relates to a process for the preparation of catalystsand, more particularly to the preparation of catalysts for use in thepolymerization of olefin oxides.

DESCRIPTION OF THE PRIOR ART

The catalytic polymerization of olefin oxides has been practiced for thepast several years, one of the commercial processes being the suspensionpolymerization of ethylene oxide in isopentane using as a catalystcalcium hexammine (Ca (NH₃)₆) modified with a mixture of propylene oxideand acetonitrile. In this process, it is believed that a living polymeris generated and is eventually terminated by impurities which build upin the medium.

Although this polymerization process has proven successful, it has acertain negative aspect which detracts from optimization and is foundboth in the polymerization process itself, the process for preparing thecatalyst, and the respective polymer and catalyst products. Among otherthings, this deficiency serves to inhibit the production of highmolecular weight polymers and polymerization productivity. It apparentlystems from an acute sensitivity to impurities and changes in operatingconditions, e.g., catalyst components and their ratios, polymerizationtime, and chemical and mechanical degradation of the polymer chain. Toovercome this deficiency, these processes have come under carefulscrutiny but improvements that avoid sensitization of the polymer orcatalyst have been few and far between apparently because of the complexmechanism of the polymerization and the complex, and still unknown,structure of the catalyst.

SUMMARY OF THE INVENTION

An object of this invention, therefore, is to provide an improvement inthe molecular weight picture and/or in productivity. To achieve thisobjective, the improvement must necessarily avoid sensitization of thepolymer or catalyst at least in those areas which will counter theproductivity increase or depress the molecular weight.

Other objects and advantages will become apparent hereinafter.

According to the present invention high molecular weights and/orproductivities are achieved by using a catalyst prepared first in theconventional manner comprising:

(i) admixing calcium, ammonia, an alkylene oxide modifier, and anorganic nitrile modifier, the alkylene oxide consisting of carbon,hydrogen, and oxirane oxygen atoms and the organic nitrile consisting ofcarbon, nitrogen, and hydrogen atoms, at least one hydrogen atom beingacidic, to form a slurry of modified calcium hexammine in ammonia; and

(ii) evaporating ammonia to provide a solid residue

and, then, carrying out the improvement which comprises:

aging the solid residue at a temperature in the range of about 150° C.to about 225° C.

The fact that the catalyst is complex, pyrophoric, air sensitive, andinsoluble in, or reactive with, most organic solvents makes chemical aswell as spectroscopic analyses difficult. Consequently, it is notsurprising that the structure of the catalyst prepared by either theconventional process or the improved process, as heretofore described,is unknown. The improved catalyst will have to be, therefore, defined bythe process by which it is made.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The catalyst, the process for making the catalyst with the nitrilemodifier, and the polymerization process as known prior to subjectinvention are described in U.S. Pat. No. 2,969,402 issued on Jan. 24,1961 to Hill et al for "Preparation of Catalysts for the Polymerizationof Epoxides", which patent is incorporated by reference herein. The term"hexammoniate" has been changed in the present specification to--hexammine--.

The temperature used in step (i) can be in the range of about minus 50°C. to about plus 25° C. and is preferably in the range of about minus40° C. to about minus 20° C. or as close as possible to minus 33.5° C.This step is carried out in the liquid phase with ammonia in the liquidstate under suitable pressure. An excess of ammonia is desirable, e.g.,about 12 to about 125 moles of ammonia per gram atom of calcium. Theammonia is essentially anhydrous. Two modifiers are also introduced instep (i). One of the modifiers is an alkylene oxide consisting ofcarbon, hydrogen, and oxirane oxygen atoms. Although the number ofcarbon atoms in the alkylene oxide can range from 2 to about 20 orhigher, alkylene oxides having 2 to about 5 carbon atoms are preferred,e.g., ethylene oxide, propylene oxide, 1,2-epoxybutane, and2,3-epoxybutane. The second modifier is an organic nitrile consisting ofcarbon, nitrogen, and hydrogen atoms, at least one hydrogen atom beingacidic. The nitrile is preferably a saturated aliphatic mononitrilewherein the organic moiety has 2 to about 10 carbon atoms, e.g.,acetonitrile, propionitrile, and butyronitrile. Aromatic nitriles suchas benzonitrile and ortho-toluenenitrile are also useful.

The alkylene oxide can be used in a ratio of about 0.3 to about 10 molesof alkylene oxide per gram atom of calcium and the nitrile can be usedin a ratio of about 0.2 to about 0.8 mole of nitrile per gram atom ofcalcium. Preferred ratios are about 0.4 to about 1 mole of alkyleneoxide and about 0.3 to about 0.6 mole of nitrile, all per gram atom ofcalcium. Step (i) is preferably carried out with agitation, a slurry ofmodified calcium hexammine in ammonia being formed. Where an organicdiluent is present, a slurry is also formed.

The order of introduction of the calcium, the ammonia, and the modifiersin step (i) can vary. The common procedure is to conduct step (i) in twosteps, the first step being to add the calcium to the ammonia to form asolution of calcium hexammine and the second step to add the modifiers.An alternative mode is to introduce the calcium and modifiers firsttogether with a low boiling (and low freezing) organic diluent and thenadd the ammonia. The least preferred is to add the calcium to a mixtureof the ammonia and the modifiers.

The next step, step (ii) is the evaporation of ammonia to provide asolid catalyst residue. This can be accomplished by merely permittingthe catalyst slurry to come to room temperature and pressure, or theslurry may be heated gently, e.g., in a cool water bath, to bring it toroom temperature, the latter being the usual way of accomplishing theevaporation where step (i) is run at a temperature of about minus 33.5°C., which is a common operating temperature for this process step. Otherconventional evaporation or stripping techniques can be applied here.The evaporation is continued until a dry gray solid is observed where itis desired to age the dry solid. This may be done where no diluent or alow boiling organic diluent is used in step (i). Where it is desired toage the catalyst in slurry form, an organic diluent is usually addedwhen a gray pasty solid is present, again where no diluent or where alow boiler is used initially. The evaporation step is usually conductedat ambient temperatures where no organic diluent is present, or it canbe conducted at, or slightly higher than, the boiling point of the lowboiling diluent if one is used. It can be carried out in the temperaturerange between the boiling point of ammonia (minus 33.5° C.) and about100° C., however. The aging step can be conducted on the dry solid orthe slurry with no appreciable difference in result.

It is desirable to carry out at least part of the process, or all of theprocess, in an inert organic liquid diluent, the most preferablecondition being when the final catalyst product is in slurry form fortransfer to, and direct use, in the olefin oxide polymerization.

The alternative ways of deploying organic diluents in the subjectprocess are as follows:

(a) prepare a dry or pasty solid, slurry with a high or intermediateboiler (using medium stirring), and age;

(b) same as (a) except slurry concurrently with evaporation of ammonia;

(c) carry out the first step in a low boiling, low freezing, organicdiluent; strip off ammonia and low boiler to provide dry solid; and age;and

(d) same as (c) except slurry solid during or after stripping with ahigh boiler, i.e., a diluent which will not boil off during aging, or anintermediate boiler.

The organic diluent referred to above is one which is inert to any ofthe reactants or the catalyst product and will not be affected byoperating conditions except, of course, in cases where it is to bestripped. If the diluent will be used to form the slurry used in thepolymerization, it also should be inert to the polymerization reactantsand product and the polymerization operating conditions.

The low boiling diluents are exemplified by the C₅ and C₆ hydrocarbonssuch as isopentane and hexane. They have low freezing points and arereadily stripped during the evaporation step. The high boiling diluentsare represented by the C₁₂ to C₁₉ hydrocarbons, e.g., dodecane andhexadecane. Intermediate boiling diluents are the C₇ to C₉ hydrocarbonssuch as heptane and isooctane. The intermediate boilers have lowfreezing points so that they will not freeze during the stripping step(step (ii)). These intermediate boilers are the choice for continuousplant processes where pressure equipment is available, and are utilizedthroughout the catalyst process and the polymerization. One advantage ofusing the inert diluents is in the realm of safety in view of thepyrophoric and air sensitive nature of the catalyst.

As noted, the invention lies in aging the dry catalyst or catalystslurry at a temperature in the range of about 150° C. to about 225° C.and preferably in the range of about 200° C. to about 225° C. The agingstep may be carried out for about 1 to about 15 or more hrs. below about200° C. and preferably for no more than about 5 or even 3 hrs. aboveabout 200° C. At the end of the aging period the catalyst is cooled toroom temperature by air quenching or any other conventional quenchingmeans.

Throughout the preparation of the catalyst, conventional precautions aretaken to exclude water, oxygen, and carbon dioxide from the system. Thismay be accomplished by using properly sealed apparatus together with aninert atmosphere such as nitrogen. The inert gas can be used first as asweep and then the process steps can be conducted in the sameatmosphere.

The finished catalyst in dry or slurry form is then used in theconventional polymerization process. A typical polymerization isdescribed in Example 1. A broad range of olefin oxides and mixtures ofolefin oxides can be used, e.g., having 2 to about 20 carbon atoms. Apreferred monomer is ethylene oxide. Polymerization temperatures can bein the range of about minus 30° C. to about 150° C., a preferred rangefor ethylene oxide monomer being about 0° C. to about 60° C. It isgenerally carried out in an inorganic diluent with agitation and in aninert atmosphere such as nitrogen to exclude oxygen and carbon dioxide.A catalyst concentration in the range of about 0.02 to about 10 percentby weight based on the weight of the olefin oxide feed can be used.Polymerization times can be run from minutes to days depending on theconditions used. Preferred times are about 1 to about 10 hours.

The molecular weights of the various polymers produced by theconventional polymerization process described in more detail hereafterin the examples are approximated by measuring their solution viscositiesusing a Brookfield viscometer. The solution viscosities are measured as1% or 5% solutions of polymer in water and are expressed in units of CPS(centipoise). Solution viscosities are correlated with molecular weightsvia their intrinsic viscosities using the relationship:

[eta]=6.4×10⁻⁵ Mw⁰.82 in water at 35° C. wherein Mw is weight averagemolecular weight. Conventional polymers are available in molecularweights ranging from 100,000 to greater than 6 million. With the highermolecular weight resins, viscosity measurements are complicated becauseof the difficulties encountered in dissolving the resins. Duringdissolution the mixture assumes a mucous-like consistency with a hightendency to gel. In addition, the extremely long chains are quitesensitive to shearing forces and must be stirred under very low shearingconditions in order to minimize mechanical degradation. The procedurefor dissolving these resins may be found in Bulletin numbered F 42993 ofMay, 1970 published by the Union Carbide Corporation and entitled, "Howto Dissolve Polyox Water-Soluble Resins.

The following examples illustrate the invention:

EXAMPLE 1

Redistilled calcium turnings are added to liquid anhydrous ammonia in avessel which is maintained at atmospheric pressure and about minus 33.5°C. The molar ratio of ammonia to calcium is noted below. The vessel ispreviously swept with nitrogen and a nitrogen atmosphere maintained.Agitation is used throughout the procedure. A solution is formed, whichtakes on a blue color. The modifiers; propylene oxide and acetonitrile,are then added and the blue color changes to gray and a slurry isformed. The molar ratio of calcium to modifiers is 1:1 and the molarratio of propylene oxide to acetonitrile is 3:2. Ammonia is stripped offat temperatures up to 96° C. for about 3 hours and the solid is eitherunaged, aged in the dry state, or slurried with a high boiler and agedbefore use in the polymerization. Aging is accomplished at a certaintemperature for a certain number of hours hereinafter noted.

The polymerization is typical of the conventional polymerizations usedfor olefin oxides. It is carried out in a stirred reactor by chargingthe dry catalyst or catalyst slurry. The monomer, ethylene oxide, is fedon demand so as to maintain a 31° C. reaction temperature. Heat exchangeis controlled by reflux cooling of the diluent and the system iscontinuously purged with nitrogen. The reaction is carried out for acertain length of time, noted below, after which the slurry iscentrifuged and the resin product is dried. The polymer is treated withCO₂ to minimize polymer degradation and with 0.5 percent anhydrous andparticulate colloidal silica to inhibit agglomeration. About 8 percentby weight concentration of monomer is maintained throughout thepolymerization. The productivity is measured by determining the numberof parts by weight of polymer product per part by weight of calciumpresent in the catalyst. The solution viscosity is given in CPS andbased on a one percent solution at 25° C. as discussed above using aBrookfield Viscometer RVF 2/2.

Variables and results in this example 1 are as follows:

(a) The high boiler is dodecane.

(b) The molar ratio of ammonia to calcium is 100:1.

(c) Aging temperature: 200° C.

(d) Slurry used in aging and polymerization.

(e) Polymerization time: 1 hour.

(f) A catalyst is prepared and four samples are used, one in each offour polymerizations. Aging times and productivities are as follows:

    ______________________________________                                        Sample      Aging Time Productivity                                           ______________________________________                                        1           unaged     187                                                    2           1 hour     250                                                    3           2 hours    421                                                    4           3 hours    436                                                    ______________________________________                                    

EXAMPLE 2

Example 1 is repeated except as follows:

(a) No organic diluent is used.

(b) The molar ratio of ammonia to calcium is 50:1.

(c) Aging temperature: see below.

(d) Dry solid used in aging and polymerization.

(f) Two catalysts are prepared to provide three samples each; one sampleis used in each of six polymerizations. Aging time is one hour. Agingtemperatures and productivities are as follows:

    ______________________________________                                        Sample    Aging Temperature °C.                                                                  Productivity                                        ______________________________________                                        First Catalyst                                                                1         unaged          259                                                 2         200             447                                                 3         250             172                                                 Second Catalyst                                                               1         unaged          250                                                 2         200             432                                                 3         250             68                                                  ______________________________________                                    

EXAMPLE 3

Example 2 is repeated except as follows:

(a) The high boiler is dodecane except as noted below.

(d) Slurry is used in aging and polymerization except as noted below.

(f) A catalyst is prepared and five samples are used, one in each offive polymerizations. Aging time is three hours. Aging temperatures andproductivities are as follows:

    ______________________________________                                        Sample    Aging Temperature °C.                                                                  Productivity                                        ______________________________________                                        1         unaged          303                                                 2         175             328                                                 3         200             558                                                 4         217             743                                                 5         250 (dry solid) 44                                                  ______________________________________                                    

EXAMPLE 4

Example 3 is repeated except as follows:

(c) Aging temperature: 200° C.

(f) Four catalysts are prepared to provide two samples each for thefirst two polymerizations and three samples each for the second twopolymerizations. Aging times and productivities are as follows:

    ______________________________________                                        Sample     Aging Time     Productivity                                        ______________________________________                                         First Catalyst                                                               1          unaged         259                                                 2          2 hours        447                                                 Second Catalyst                                                               1          unaged         250                                                 2          2 hours        432                                                 Third Catalyst                                                                1          unaged         154                                                 2          one hour (dry solid)                                                                         221                                                 3          one hour       244                                                 Fourth Catalyst                                                               1          unaged         303                                                 2          one hour       492                                                 3          three hours    558                                                 ______________________________________                                    

EXAMPLE 5

Example 1 is repeated except as follows:

(e) Polymerization time: see below.

(f) A catalyst is prepared and two samples are used, one in each of twopolymerizations. Aging time is 3 hours for both samples. Polymerizationtimes, productivities and solution viscosities follow:

    ______________________________________                                                                           Solution                                   Sample Polymerization Time                                                                           Productivity                                                                              Viscosity                                  ______________________________________                                        1      1                532        12,500                                     2      6               1917        16,360                                     ______________________________________                                    

EXAMPLE 6

Example 2 is repeated except as follows:

(a) Same except as noted below.

(c) Aging temperature: 200° C.

(d) Same except as noted below.

(e) Polymerization times noted below.

(f) Four catalysts are prepared to provide eight samples, one for eachpolymerization. Aging times, polymerization times, and solutionviscosities are as follows:

    ______________________________________                                                                           Solution                                   Sample Aging Time  Polymerization Time                                                                           Viscosity                                  ______________________________________                                        First Catalyst                                                                1      unaged      1 hour          3720                                                          6 hours         6000                                       2      1 hour      1 hour          9540                                                          6 hours         17,700                                     Second Catalyst                                                               1      unaged      1 hour          1720                                                          6 hours         3380                                       2      1 hour      1 hour          4880                                                          6 hours         8340                                       Third Catalyst*                                                               1      unaged      1 hour          4080                                                          6 hours         7980                                       2      three hours 1 hour          10,120                                                        31/2 hours      16,180                                     Fourth Catalyst*                                                              1      unaged      6 hours         10,700                                     2      three hours 6 hours         16,040                                     ______________________________________                                         *Aging and polymerization conducted with dodecane slurry.                

EXAMPLE 7

Example 3 is repeated except as follows:

(a) The high boiler is a mixture of C₁₃ and C₁₄ straight chain saturatedhydrocarbons boiling in the range of about 230° C. (the C₁₃ -C₁₄ mixtureis first dried over molecular sieves and purged with nitrogen).

(c) Aging temperature: 215° C.

(f) A catalyst is prepared and three samples are used, one in each ofthree polymerizations. Aging times, polymerization times,productivities, and solution viscosities are as follows:

    ______________________________________                                                         Polymerization       Solution                                Sample                                                                              Aging Time Times       Productivity                                                                           Viscosity                               ______________________________________                                        1     unaged     1 hour      225      --                                                       6 hours     588       8,930                                  2     three hours                                                                              1 hour      625      --                                                       6 hours     1838     16,000                                  3     two cycles of                                                                            1 hour      275      --                                            three hours                                                                   each for a                                                                    total of six                                                                  hours                                                                   ______________________________________                                    

EXAMPLE 8

Example 7 is repeated except as follows:

(c) Aging temperature: 200° C.

(f) Aging time: 3 hours. A catalyst is prepared and samples used inthree polymerizations. The polymerization time is 6.5 hours. Thecombined productivity is 1388 parts by weight of polymer per part byweight of calcium and the solution viscosity is 14,680. The screenclassification of resin particle sizes is as follows:

    ______________________________________                                                         Percent Passing                                              Mesh Size        through screen                                               ______________________________________                                         10              99.57                                                         20              99.00                                                         40              95.50                                                         60              81.40                                                         80              77.60                                                        100              9.13                                                         ______________________________________                                    

Note: the small particle size over conventional operations is consideredan advantage in certain applications.

EXAMPLE 9

Example 7 is repeated except as follows:

(f) A catalyst is prepared and used in a polymerization. Aging time,polymerization times, and solution viscosity are as follows:

    ______________________________________                                                                           Solution                                   Aging Time                                                                             Polymerization Time                                                                          Productivity                                                                             Viscosity                                  ______________________________________                                        three hours                                                                            1 hour          680       --                                                  6 hours        1755       15,600                                     ______________________________________                                    

EXAMPLE 10

Example 1 is repeated except as follows:

(f) Three catalysts are prepared substituting for the acetonitrilemodifier, the modifier noted below. Aging time is one hour. Modifiersand productivities are as follows:

    ______________________________________                                                       Productivity Productivity                                      Modifier       (unaged)     (aged)                                            ______________________________________                                        benzonitrile   43           321                                               ortho-toluonitrile                                                                           60           394                                               trimethylacetonitrile                                                                        167          193                                               (no acidic hydrogen)                                                          ______________________________________                                    

EXAMPLE 11

Example 3 is repeated except as follows:

(a) Hexadecane is used instead of dodecane.

(f) A catalyst is prepared and six samples are used, one in each of sixpolymerizations. Aging time is one hour. Aging temperatures,productivities, and solution viscosities are as follows:

    ______________________________________                                                                            Solution                                  Sample Aging Temperature °C.                                                                   Productivity                                                                              Viscosity                                 ______________________________________                                        1      unaged           --          3080                                      2      150              --          4200                                      3      175              374         5500                                      4      200              507         7620                                      5      217              686         10,060                                    6      250              18          --                                        ______________________________________                                    

Polyethylene oxide plant production data indicate that by raising thecatalyst treatment temperature from 96°-97° C. to 156°-158° C., theyield of polyethylene oxide was increased an average of about 36% andthe 1% viscosity of polyethylene oxide increased about 160%. These dataare presented below:

    ______________________________________                                        Catalyst Treatment     Performance                                            Run  Temp.            Amount Used       Viscosity                             No.  °C.                                                                             Hrs     Lbs   % Ca.  Yield  1% (cps)                            ______________________________________                                        1    158      4.5     12           921    7410                                2    158      4.5     14    0.12   728    7310                                3    156      4.5     14    0.10     878.6                                                                              8200                                4    156      4.5     14    0.13   935    7920                                5    158      6.0     14.1  0.10   979    9300                                6    158      6.0     12    0.14    1166  6960                                7    158      4.5     11    0.13    1300  11920                               8    156      4.5     12    0.14   987    7400                                9    97       4.5     14    0.10   971    3390                                10   97       4.5     14    0.14   693    3100                                11   96       4.5     15    0.11   716    3258                                12   96       4.5     14    0.16   617    2825                                13   96       4.5     15    0.18   883    3263                                14   97       4.5     15    0.16   663    2847                                15   97       4.5     15    0.13   543    3708                                ______________________________________                                          Yield is defined as lbs. of polyethylene oxide produced per lb. of           catalyst used.                                                           

We claim:
 1. In a process for the polymerization of olefin oxides, theimprovement comprising carrying out the process in the presence of acatalytically active amount of the catalyst prepared by a process whichcomprises:(i) admixing calcium, ammonia, an alkylene oxide modifier andan organic nitrile modifier, the alkylene oxide consisting of carbon,hydrogen, and oxirane oxygen atoms and the organic nitrile consisting ofcarbon, nitrogen, and hydrogen atoms, at least one hydrogen atom beingacidic, to form a slurry of modified calcium hexamine in ammonia; (ii)evaporating ammonia to provide a solid residue; and (iii) aging thesolid residue at a temperature in the range of about 150° C. to about225° C.
 2. The process for the polymerization of olefin oxides definedin claim 1 in which the aging time of the solid residue is about 1 toabout 15 hours.
 3. The process defined in claim 1 in which the solidresidue is aged at a temperature wherein the lower end of the range isabout 200° C.